The present invention relates to a water mixing system for a reservoir tank.
Potable water or drinking water is distributed to residents of a city by pumping water into a reservoir tank located on a hill. When the resident needs water, the resident opens a water faucet located at the resident's home. The water faucet is connected to the reservoir tank which may be at a higher elevation than the resident. Due to water pressure, the water in the reservoir tank flows to the resident's water faucet, is dispensed and used by the resident.
In order to disinfect the water in the reservoir tank, municipalities typically introduce chlorine and sometimes ammonia into the water. To this end, a sample of the water from the reservoir tank is taken and the amount of chlorine is analyzed to derive the amount of bacteria that remains within the water. The bacteria cancel the chlorine and reduce the amount of chlorine in the water. If no chlorine is detected, then this situation indicates presence of bacteria. If too much chlorine is present in the water, then water may taste horrible and if excessive be toxic. As a result, if too much chlorine is added to the water, then the water is disinfected but tastes horrible and if excessive the water may be toxic. Conversely, if too little chlorine is added to the water, then the water may taste fine but is not disinfected.
One problem of sampling the water in the reservoir tank is the inconsistency or uneven distribution of disinfectants (e.g., chlorine) in the water that might provide a false reading or indication of the amount of disinfectants in the water. For example, the sample may be taken from the reservoir tank. Unfortunately, the amount of disinfectants in the water of the reservoir tank is not even or evenly distributed from top to bottom. The reason for the uneven distribution is that water temperature tends to stratify when in the reservoir tank. Generally, cool water resides at the bottom of the tank and warmer water resides at the top of the tank. More bacteria generally breed at the upper warmer level of the water. As such, a sample reading of the water taken at the top of the reservoir tank may indicate that there is no chlorine in the water. The excess amount of bacteria has cancelled all of the disinfectants at the warmer upper levels. In response, the municipality may insert additional chlorine into the water with the assumption that the detected amount of chlorine in the sampled water (i.e., no chlorine) is representative of the amount of chlorine throughout the reservoir tank. In one scenario, too much chlorine would be added to the water. The water may be disinfected. However, the water may taste awful or be toxic due to the excess chlorine. Please note that the amount of chlorine being measured is in the range of 2½ to 3 parts per million. Conversely, if the water sample is taken from the bottom of the reservoir tank such as through a spigot or other tube flowing or inserted at the lower levels of the water, then the sample of water taken from the cooler lower levels of the reservoir tank may indicate an excess amount of chlorine or no bacteria. The municipality may then add in too little chlorine based on the assumption that the elevated chlorine level at the lower cooler levels is representative of the chlorine level contained throughout the water. In this situation, the water may not taste like chlorine or ammonia. However, the water is not disinfected. The resident may become sick.
Another problem associated with disinfecting water in a reservoir tank is that chlorine and ammonia may mix with the water at different concentrations or efficiencies based on temperature and mixing of the water in the tank. If the water in the tank is poorly mixed, the water in the reservoir tank will have different temperatures based on the elevation and other factors. As a result, the water may be disinfected unevenly.
Yet another problem associated with disinfecting water in a reservoir tank is with the addition of ammonia to the water in the tank. A dangerous chemical reaction may occur if added chemicals are improperly mixed with the water because improper mixing may cause nitrification of the water supply making it unfit for human consumption.
The stratified temperature gradients of the water in the tank may be caused by the temperature difference from the hot sun introducing heat into the metallic reservoir tank and the cold earth or by natural convective evaporation. As such, the upper levels of the water generally are warmer than the lower levels of the water. Additionally, the temperature of the water may be stratified because warm water will tend to rise and cool water will tend to drop.
Prior art systems have been developed to de-stratify the temperature gradients in the water. Unfortunately, these prior art systems have various deficiencies. For example, these prior art systems may rest on the floor of the water tank. Over a period of time, the system vibrates on the floor of the tank and rubs off any coating on the interior side of the tank which would have to be replaced over a period of time. Additionally, these prior art systems may be difficult to install and maintain. In particular, some prior art systems require an underwater diver to dive into the water to set up the mixing unit. Unfortunately, the cost to hire an underwater diver, disinfect the underwater diver and other costs associated with using the underwater diver may be expensive. Another deficiency in the prior art systems is that the speed at which the systems destratify the temperature gradients in the water is slow and not responsive enough. Hence, there is a need in the art for an improved system for mixing water or de-stratifying temperature gradients in water stored within a reservoir tank.